A 164-dBΩ Transimpedance Amplifier for Monolithic CMOS-MEMS Oscillators in Biosensing Applications

Abstract

This article presents a fully differential tunable high-gain transimpedance amplifier (TIA) conceived as front-end circuit for monolithic CMOS-MEMS resonators operating in self-sustained oscillation mode. The proposed solution is based on a capacitive feedback network topology using a varactor for gain control. The design is specifically oriented to CMOS-MEMS biosensing applications that require post-CMOS MEMS processing. The adoption of a TIA solution provides robustness against one of such processing steps (i.e., oxygen plasma activation) and a 10 improvement in feedthrough signal elimination compared to a single-ended alternative. The ASIC was fabricated using a 0.35-µm commercial CMOS technology from Austria Microsystems featuring a maximum transimpedance gain of 164 dBΩ with a 10-dB tuning range. It operates at frequencies up to 10 MHz with an input-referred current noise density as low as 13 fA•Hz -1/2 providing an exceptional high-performance sensing. With a 3.3 V supply voltage, it exhibits a 1.6 mW power consumption. The presented TIA was integrated on-chip with various MEMS resonator topologies, either oriented to volatile organic compounds (VOCs) detection or to microfluidics integration for Lab-on-Chip (LoC) systems, corroborating self-sustained oscillation with a 135-ppb measured Allan deviation and 1.1 V output voltage swing.INDEX TERMS CMOS-MEMS oscillator, transimpedance amplifier (TIA), Lab-on-Chip (LoC), ASIC. TABLE I LIST OF ABBREVIATIONS AND ACRONYMS USED IN THIS WORK